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Title: Comparison of the Core-collapse Evolution of Two Nearly Equal-mass Progenitors

We compare the core-collapse evolution of a pair of 15.8Mstars with significantly different internal structures, a consequence of the bimodal variability exhibited by massive stars during their late evolutionary stages. The 15.78 and 15.79Mprogenitors have core masses (masses interior to an entropy of 4kBbaryon−1) of 1.47 and 1.78Mand compactness parametersξ1.75of 0.302 and 0.604, respectively. The core-collapse simulations are carried out in 2D to nearly 3 s postbounce and show substantial differences in the times of shock revival and explosion energies. The 15.78Mmodel begins exploding promptly at 120 ms postbounce when a strong density decrement at the Si–Si/O shell interface, not present in the 15.79Mprogenitor, encounters the stalled shock. The 15.79Mmodel takes 100 ms longer to explode but ultimately produces a more powerful explosion. Both the larger mass accretion rate and the more massive core of the 15.79Mmodel during the first 0.8 s postbounce time result in largerνe/ν¯eluminosities and RMS energies along with a flatter and higher-density heating region. The more-energetic explosion of the 15.79Mmodel resulted in the ejection of twice as much56Ni. Most of the ejecta in both models are moderately proton rich, though counterintuitively the highest electron fraction (Ye= 0.61) ejecta in either model are in the less-energetic 15.78Mmodel, while the lowest electron fraction (Ye= 0.45) ejecta in either model are in the 15.79Mmodel.

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DOI PREFIX: 10.3847
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Journal Name:
The Astrophysical Journal
Medium: X Size: Article No. 35
Article No. 35
Sponsoring Org:
National Science Foundation
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